A display device having a through-hole formed on a part of a display area is described in Patent Documents 1 and 2. This display device uses an edge-type backlight, which has a through-hole formed at a location corresponding to the location of a display area. According to the display device, luminance irregularity around the through-hole can be reduced.    [Patent document 1] WO 2017/061312    [Patent Document 2] Japanese Unexamined Patent Application Publication No. 2017-102452
In an ordinary backlight having a through-hole, as shown in FIG. 9, light L1 emitted from light sources 81 is reflected on the end face of a through-hole 83. As a result, light from the light sources 81 hardly reaches an area 70 located opposite to the light sources 81 with respect to the through-hole 83. This makes the area 70 darker than an area near the light source 81. Meanwhile, light L2 from the light source 81 propagates to an area around the area 70 and therefore gives the area 75 luminance equal to the luminance of the area near the light source 81. In this manner, this backlight poses a problem that the luminance of the area 70 becomes lower than the luminance of the area 75 to create luminance irregularity. This problem occurs particularly in a case where the light sources 81 are arranged on one side of a light guide element 82.